I get asked all the time, "what type of wire do you use to build the cables?".  Some guys want marine grade wire or they heard that welding cable is the hot set up.  Below is a description of what we use and my opinions about if you should use be using marine grade wire on your Dodge Dart.

SGT Battery Cable:

We generally use SAE (Society of Automotive Engineers) SGT battery cable.  SGT designates the type of wire.  For example THHN is probably what you have wiring your house.  SGT is self extinguishing PVC insulation rated at 50 Volts.  It's typically rated for 85 or 105 degrees C.  This is the lowest cost wire of the 3 wire types discussed here and it does the job just fine.  The strands are larger than the other two, making the wire stiffer so it stays where you put it but still flexible enough to bend around tight corners. 

Pros: Lowest cost, SAE rating. 
Cons: Lowest temp rating (as low as 85C, about 185F).

SGX Battery Cable:

Sometimes we use SGX battery cable.  SGX uses a XLP insulation which has a higher temperature rating.  The trade off is the insulation is thicker and stiffer.  Often it has a higher strand count to make it flexible to help offset the stiffer insulation.  It also costs more. If you need the higher temp rating, it might be a good solution. 

Pros: SAE rating.  Higher temp rating (125C).
Cons: Stiffer, might be harder to route. More expensive.

Marine Grade:

There are several types of "Marine" wire.  It's usually rated for a higher temperature and "wet" (think submersed) applications. it is also has a requirement that it be "self-extinguishing".  That is extremely important on a boat in the middle of nowhere. SGT-M is SGT battery cable rated for marine use and is only a little more expensive than SGT.  Some  marine grade wire is "tinned" (plated) to help reduce corrosion and has a high strand count like welding cable.  it can get very expensive (twice as much).

 There was a time, when I was grumpier, when asked for a marine cable for a car that I would answer "Are you going to be taking your Taurus out to sea??".  I thought it was a waste of time, money and energy.  I still do in most cases.  Then a friend pointed out that perhaps marine cable would help if one lived somewhere near the ocean and a salt atmosphere, or maybe salt on the roads.  Or perhaps the self-extinguishing characteristic was of critical importance to the customer.  I  guess that might be true.  I live in the desert so I don't have any personal experience with such things.  However, I can tell you that once we install the lugs, terminals and the heat shrink is applied, no copper is exposed so I honestly doubt it actually makes much difference in automotive applications.

Because of the high cost I only stock small quantities of marine cable but if I don't have it, I can order it.  Expect it to take a couple weeks longer.